The present invention generally relates to apparatus and methods for the processing of wastewater and, more specifically, to an improved salt crystallizer system that permits the recovery of essentially 100% of water and that is suitable in a microgravity environment.
In both terrestrial and non-terrestrial closed environments, wastewater may require processing as a result of a limited water supply. In the context of outer space, the amount of water that must be carried on a space flight represents a potential for additional weight. While more water can lead to a longer mission, there is greater fuel cost for the additional weight. In order to minimize the amount of needed water, wastewater can be processed to useable water. To remove organic compounds from the wastewater, bioreactors or bioprocessors have utilized aerobic and/or anaerobic processes. However, even though bioreactors remove the organic compounds, inorganic compounds, such as salts, remain in the wastewater. These, too, must be removed in order to make the wastewater useable.
Although not necessarily used in outer space, salt crystallizers have been devised to recover salts. For example, in U.S. Pat. No. 3,977,835, it was noted that existing processes only separate efficiently portions of the contained salt and result in the loss of desired salts. The inventive process was directed towards recovering salts rich in potassium. This was accomplished by first cooling the brine to crystallize mirabilite. The brine was then evaporated in a first solar evaporator to crystallize out sodium salts that are free of potassium salts. Next, the brine was evaporated in a second solar evaporator to crystallize a group of salts rich in potassium. While the process may be useful to recover particular salts, it does require multiple steps. And it may not likely provide the ability to discard or remove salts and allow recovery of about 100% water.
U.S. Pat. No. 4,547,197 discloses a process for recovering sodium chloride from brine. The process includes removing excess secondary salts from the brine by evaporation and then re-evaporating the brine without disturbing the balance of the secondary salts. Doing so allows a maximum amount of the sodium chloride to be recovered. More specifically, in the initial evaporation, in order to prevent the crystallization of higher solubility components with the sodium chloride, the concentrations of such components are controlled to remain below their saturation. A major part of the sodium chloride is extracted as a crystallized product and water is extracted as steam. The brine then undergoes flash evaporation to further crystallize out sodium chloride and other salts. Thereafter, the mixture of salts, including sodium chloride, are dissolved in water and returned to mix with additional brine at the initial step of evaporation. As can be seen, crystallization occurs in multiple steps, leading to a more complex design. Also, water is not being recovered, but rather discarded.
As can be seen, there is a need for an apparatus and method for removing salts from wastewater and recovering water. Also needed is an apparatus and method for removing salts from wastewater in a fashion that is simple yet efficient. A further need is for an apparatus and method that recovers almost 100% water from wastewater. An additional need is to remove salts from wastewater in a closed environment and in a microgravity environment.
In one aspect of the present invention, a water reclamation system for a closed environment comprises: a mixer that receives a brine; a processor downstream of the mixer, with the processor distilling water from the brine and; a crystallizer subsystem downstream of the processor, with the crystallizer subsystem crystallizing salt from the brine and recycling the brine to the mixer.
In another aspect of the present invention, a method of reclaiming water in a closed environment comprises: mixing in a mixer an input brine with a recycle brine; distilling in a processor a substantially salt-free water from the input brine, with the processor being disposed downstream of the mixer; crystallizing in a crystallizer subsystem a salt from the input brine, with the subsystem being disposed downstream of the processor; and flowing the recycle brine from the crystallizer subsystem to the mixer.